The invention relates to a temperature-dependently controllable fluid friction clutch, particularly for a radiator fan of a motor vehicle.
From Federal German Publication Specification No. 3,122,960 a temperature-dependently controllable fluid friction clutch for the cooling fan of a motor vehicle is known in which a housing carrying the fan blades is mounted rotatably on a drive shaft. The housing is divided by a partition into a reservoir for shear fluid and an axially adjacent working chamber. In the working chamber there is arranged a rotor held on the drive shaft, which rotor together with the housing forms at least one shear gap. Within the housing a control device is arranged which controls the flow circulation of the shear fluid between the reservoir and the working chamber. A bimetallic element arranged on an end wall outside the housing acts upon the control device through a pin guided axially displaceably in an opening of the end wall. The control device comprises a valve arranged in the reservoir which blocks the shear fluid circulation to disconnect the clutch and frees it to engage the clutch.
The pin is axially displaceable in a bore of the end wall of the housing and is sealed off from the housing by a gasket seated in an annular groove in the bore. The seal firstly prevents the penetration of dirt into the interior of the housing and secondly prevents the escape of shear fluid, for example during transport of the clutch before it is installed. By reason of its friction the gasket has an unfavorable effect upon the actuation behavior of the clutch and prevents a pressure equalization between the reservoir and the atmosphere.
The present invention provides a temperature-controlled fluid friction clutch the actuation behavior of which is not impaired by the sealing of the pin of the temperature-control device.